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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2011 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.util.concurrent;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import com.google.common.annotations.Beta;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import com.google.common.annotations.GwtCompatible;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.base.Function;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.collect.Maps;<a name="line.24"></a>
<span class="sourceLineNo">025</span><a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.util.Collections;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import java.util.Map;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.util.concurrent.ConcurrentHashMap;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.util.concurrent.atomic.AtomicLong;<a name="line.29"></a>
<span class="sourceLineNo">030</span><a name="line.30"></a>
<span class="sourceLineNo">031</span>/**<a name="line.31"></a>
<span class="sourceLineNo">032</span> * A map containing {@code long} values that can be atomically updated. While writes to a<a name="line.32"></a>
<span class="sourceLineNo">033</span> * traditional {@code Map} rely on {@code put(K, V)}, the typical mechanism for writing to this map<a name="line.33"></a>
<span class="sourceLineNo">034</span> * is {@code addAndGet(K, long)}, which adds a {@code long} to the value currently associated with<a name="line.34"></a>
<span class="sourceLineNo">035</span> * {@code K}. If a key has not yet been associated with a value, its implicit value is zero.<a name="line.35"></a>
<span class="sourceLineNo">036</span> *<a name="line.36"></a>
<span class="sourceLineNo">037</span> * &lt;p&gt;Most methods in this class treat absent values and zero values identically, as individually<a name="line.37"></a>
<span class="sourceLineNo">038</span> * documented. Exceptions to this are {@link #containsKey}, {@link #size}, {@link #isEmpty},<a name="line.38"></a>
<span class="sourceLineNo">039</span> * {@link #asMap}, and {@link #toString}.<a name="line.39"></a>
<span class="sourceLineNo">040</span> *<a name="line.40"></a>
<span class="sourceLineNo">041</span> * &lt;p&gt;Instances of this class may be used by multiple threads concurrently. All operations are<a name="line.41"></a>
<span class="sourceLineNo">042</span> * atomic unless otherwise noted.<a name="line.42"></a>
<span class="sourceLineNo">043</span> *<a name="line.43"></a>
<span class="sourceLineNo">044</span> * &lt;p&gt;&lt;b&gt;Note:&lt;/b&gt; If your values are always positive and less than 2^31, you may wish to use a<a name="line.44"></a>
<span class="sourceLineNo">045</span> * {@link com.google.common.collect.Multiset} such as<a name="line.45"></a>
<span class="sourceLineNo">046</span> * {@link com.google.common.collect.ConcurrentHashMultiset} instead.<a name="line.46"></a>
<span class="sourceLineNo">047</span> *<a name="line.47"></a>
<span class="sourceLineNo">048</span> * &lt;b&gt;Warning:&lt;/b&gt; Unlike {@code Multiset}, entries whose values are zero are not automatically<a name="line.48"></a>
<span class="sourceLineNo">049</span> * removed from the map. Instead they must be removed manually with {@link #removeAllZeros}.<a name="line.49"></a>
<span class="sourceLineNo">050</span> *<a name="line.50"></a>
<span class="sourceLineNo">051</span> * @author Charles Fry<a name="line.51"></a>
<span class="sourceLineNo">052</span> * @since 11.0<a name="line.52"></a>
<span class="sourceLineNo">053</span> */<a name="line.53"></a>
<span class="sourceLineNo">054</span>@Beta<a name="line.54"></a>
<span class="sourceLineNo">055</span>@GwtCompatible<a name="line.55"></a>
<span class="sourceLineNo">056</span>public final class AtomicLongMap&lt;K&gt; {<a name="line.56"></a>
<span class="sourceLineNo">057</span>  private final ConcurrentHashMap&lt;K, AtomicLong&gt; map;<a name="line.57"></a>
<span class="sourceLineNo">058</span><a name="line.58"></a>
<span class="sourceLineNo">059</span>  private AtomicLongMap(ConcurrentHashMap&lt;K, AtomicLong&gt; map) {<a name="line.59"></a>
<span class="sourceLineNo">060</span>    this.map = checkNotNull(map);<a name="line.60"></a>
<span class="sourceLineNo">061</span>  }<a name="line.61"></a>
<span class="sourceLineNo">062</span><a name="line.62"></a>
<span class="sourceLineNo">063</span>  /**<a name="line.63"></a>
<span class="sourceLineNo">064</span>   * Creates an {@code AtomicLongMap}.<a name="line.64"></a>
<span class="sourceLineNo">065</span>   */<a name="line.65"></a>
<span class="sourceLineNo">066</span>  public static &lt;K&gt; AtomicLongMap&lt;K&gt; create() {<a name="line.66"></a>
<span class="sourceLineNo">067</span>    return new AtomicLongMap&lt;K&gt;(new ConcurrentHashMap&lt;K, AtomicLong&gt;());<a name="line.67"></a>
<span class="sourceLineNo">068</span>  }<a name="line.68"></a>
<span class="sourceLineNo">069</span><a name="line.69"></a>
<span class="sourceLineNo">070</span>  /**<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * Creates an {@code AtomicLongMap} with the same mappings as the specified {@code Map}.<a name="line.71"></a>
<span class="sourceLineNo">072</span>   */<a name="line.72"></a>
<span class="sourceLineNo">073</span>  public static &lt;K&gt; AtomicLongMap&lt;K&gt; create(Map&lt;? extends K, ? extends Long&gt; m) {<a name="line.73"></a>
<span class="sourceLineNo">074</span>    AtomicLongMap&lt;K&gt; result = create();<a name="line.74"></a>
<span class="sourceLineNo">075</span>    result.putAll(m);<a name="line.75"></a>
<span class="sourceLineNo">076</span>    return result;<a name="line.76"></a>
<span class="sourceLineNo">077</span>  }<a name="line.77"></a>
<span class="sourceLineNo">078</span><a name="line.78"></a>
<span class="sourceLineNo">079</span>  /**<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * Returns the value associated with {@code key}, or zero if there is no value associated with<a name="line.80"></a>
<span class="sourceLineNo">081</span>   * {@code key}.<a name="line.81"></a>
<span class="sourceLineNo">082</span>   */<a name="line.82"></a>
<span class="sourceLineNo">083</span>  public long get(K key) {<a name="line.83"></a>
<span class="sourceLineNo">084</span>    AtomicLong atomic = map.get(key);<a name="line.84"></a>
<span class="sourceLineNo">085</span>    return atomic == null ? 0L : atomic.get();<a name="line.85"></a>
<span class="sourceLineNo">086</span>  }<a name="line.86"></a>
<span class="sourceLineNo">087</span><a name="line.87"></a>
<span class="sourceLineNo">088</span>  /**<a name="line.88"></a>
<span class="sourceLineNo">089</span>   * Increments by one the value currently associated with {@code key}, and returns the new value.<a name="line.89"></a>
<span class="sourceLineNo">090</span>   */<a name="line.90"></a>
<span class="sourceLineNo">091</span>  public long incrementAndGet(K key) {<a name="line.91"></a>
<span class="sourceLineNo">092</span>    return addAndGet(key, 1);<a name="line.92"></a>
<span class="sourceLineNo">093</span>  }<a name="line.93"></a>
<span class="sourceLineNo">094</span><a name="line.94"></a>
<span class="sourceLineNo">095</span>  /**<a name="line.95"></a>
<span class="sourceLineNo">096</span>   * Decrements by one the value currently associated with {@code key}, and returns the new value.<a name="line.96"></a>
<span class="sourceLineNo">097</span>   */<a name="line.97"></a>
<span class="sourceLineNo">098</span>  public long decrementAndGet(K key) {<a name="line.98"></a>
<span class="sourceLineNo">099</span>    return addAndGet(key, -1);<a name="line.99"></a>
<span class="sourceLineNo">100</span>  }<a name="line.100"></a>
<span class="sourceLineNo">101</span><a name="line.101"></a>
<span class="sourceLineNo">102</span>  /**<a name="line.102"></a>
<span class="sourceLineNo">103</span>   * Adds {@code delta} to the value currently associated with {@code key}, and returns the new<a name="line.103"></a>
<span class="sourceLineNo">104</span>   * value.<a name="line.104"></a>
<span class="sourceLineNo">105</span>   */<a name="line.105"></a>
<span class="sourceLineNo">106</span>  public long addAndGet(K key, long delta) {<a name="line.106"></a>
<span class="sourceLineNo">107</span>    outer: for (;;) {<a name="line.107"></a>
<span class="sourceLineNo">108</span>      AtomicLong atomic = map.get(key);<a name="line.108"></a>
<span class="sourceLineNo">109</span>      if (atomic == null) {<a name="line.109"></a>
<span class="sourceLineNo">110</span>        atomic = map.putIfAbsent(key, new AtomicLong(delta));<a name="line.110"></a>
<span class="sourceLineNo">111</span>        if (atomic == null) {<a name="line.111"></a>
<span class="sourceLineNo">112</span>          return delta;<a name="line.112"></a>
<span class="sourceLineNo">113</span>        }<a name="line.113"></a>
<span class="sourceLineNo">114</span>        // atomic is now non-null; fall through<a name="line.114"></a>
<span class="sourceLineNo">115</span>      }<a name="line.115"></a>
<span class="sourceLineNo">116</span><a name="line.116"></a>
<span class="sourceLineNo">117</span>      for (;;) {<a name="line.117"></a>
<span class="sourceLineNo">118</span>        long oldValue = atomic.get();<a name="line.118"></a>
<span class="sourceLineNo">119</span>        if (oldValue == 0L) {<a name="line.119"></a>
<span class="sourceLineNo">120</span>          // don't compareAndSet a zero<a name="line.120"></a>
<span class="sourceLineNo">121</span>          if (map.replace(key, atomic, new AtomicLong(delta))) {<a name="line.121"></a>
<span class="sourceLineNo">122</span>            return delta;<a name="line.122"></a>
<span class="sourceLineNo">123</span>          }<a name="line.123"></a>
<span class="sourceLineNo">124</span>          // atomic replaced<a name="line.124"></a>
<span class="sourceLineNo">125</span>          continue outer;<a name="line.125"></a>
<span class="sourceLineNo">126</span>        }<a name="line.126"></a>
<span class="sourceLineNo">127</span><a name="line.127"></a>
<span class="sourceLineNo">128</span>        long newValue = oldValue + delta;<a name="line.128"></a>
<span class="sourceLineNo">129</span>        if (atomic.compareAndSet(oldValue, newValue)) {<a name="line.129"></a>
<span class="sourceLineNo">130</span>          return newValue;<a name="line.130"></a>
<span class="sourceLineNo">131</span>        }<a name="line.131"></a>
<span class="sourceLineNo">132</span>        // value changed<a name="line.132"></a>
<span class="sourceLineNo">133</span>      }<a name="line.133"></a>
<span class="sourceLineNo">134</span>    }<a name="line.134"></a>
<span class="sourceLineNo">135</span>  }<a name="line.135"></a>
<span class="sourceLineNo">136</span><a name="line.136"></a>
<span class="sourceLineNo">137</span>  /**<a name="line.137"></a>
<span class="sourceLineNo">138</span>   * Increments by one the value currently associated with {@code key}, and returns the old value.<a name="line.138"></a>
<span class="sourceLineNo">139</span>   */<a name="line.139"></a>
<span class="sourceLineNo">140</span>  public long getAndIncrement(K key) {<a name="line.140"></a>
<span class="sourceLineNo">141</span>    return getAndAdd(key, 1);<a name="line.141"></a>
<span class="sourceLineNo">142</span>  }<a name="line.142"></a>
<span class="sourceLineNo">143</span><a name="line.143"></a>
<span class="sourceLineNo">144</span>  /**<a name="line.144"></a>
<span class="sourceLineNo">145</span>   * Decrements by one the value currently associated with {@code key}, and returns the old value.<a name="line.145"></a>
<span class="sourceLineNo">146</span>   */<a name="line.146"></a>
<span class="sourceLineNo">147</span>  public long getAndDecrement(K key) {<a name="line.147"></a>
<span class="sourceLineNo">148</span>    return getAndAdd(key, -1);<a name="line.148"></a>
<span class="sourceLineNo">149</span>  }<a name="line.149"></a>
<span class="sourceLineNo">150</span><a name="line.150"></a>
<span class="sourceLineNo">151</span>  /**<a name="line.151"></a>
<span class="sourceLineNo">152</span>   * Adds {@code delta} to the value currently associated with {@code key}, and returns the old<a name="line.152"></a>
<span class="sourceLineNo">153</span>   * value.<a name="line.153"></a>
<span class="sourceLineNo">154</span>   */<a name="line.154"></a>
<span class="sourceLineNo">155</span>  public long getAndAdd(K key, long delta) {<a name="line.155"></a>
<span class="sourceLineNo">156</span>    outer: for (;;) {<a name="line.156"></a>
<span class="sourceLineNo">157</span>      AtomicLong atomic = map.get(key);<a name="line.157"></a>
<span class="sourceLineNo">158</span>      if (atomic == null) {<a name="line.158"></a>
<span class="sourceLineNo">159</span>        atomic = map.putIfAbsent(key, new AtomicLong(delta));<a name="line.159"></a>
<span class="sourceLineNo">160</span>        if (atomic == null) {<a name="line.160"></a>
<span class="sourceLineNo">161</span>          return 0L;<a name="line.161"></a>
<span class="sourceLineNo">162</span>        }<a name="line.162"></a>
<span class="sourceLineNo">163</span>        // atomic is now non-null; fall through<a name="line.163"></a>
<span class="sourceLineNo">164</span>      }<a name="line.164"></a>
<span class="sourceLineNo">165</span><a name="line.165"></a>
<span class="sourceLineNo">166</span>      for (;;) {<a name="line.166"></a>
<span class="sourceLineNo">167</span>        long oldValue = atomic.get();<a name="line.167"></a>
<span class="sourceLineNo">168</span>        if (oldValue == 0L) {<a name="line.168"></a>
<span class="sourceLineNo">169</span>          // don't compareAndSet a zero<a name="line.169"></a>
<span class="sourceLineNo">170</span>          if (map.replace(key, atomic, new AtomicLong(delta))) {<a name="line.170"></a>
<span class="sourceLineNo">171</span>            return 0L;<a name="line.171"></a>
<span class="sourceLineNo">172</span>          }<a name="line.172"></a>
<span class="sourceLineNo">173</span>          // atomic replaced<a name="line.173"></a>
<span class="sourceLineNo">174</span>          continue outer;<a name="line.174"></a>
<span class="sourceLineNo">175</span>        }<a name="line.175"></a>
<span class="sourceLineNo">176</span><a name="line.176"></a>
<span class="sourceLineNo">177</span>        long newValue = oldValue + delta;<a name="line.177"></a>
<span class="sourceLineNo">178</span>        if (atomic.compareAndSet(oldValue, newValue)) {<a name="line.178"></a>
<span class="sourceLineNo">179</span>          return oldValue;<a name="line.179"></a>
<span class="sourceLineNo">180</span>        }<a name="line.180"></a>
<span class="sourceLineNo">181</span>        // value changed<a name="line.181"></a>
<span class="sourceLineNo">182</span>      }<a name="line.182"></a>
<span class="sourceLineNo">183</span>    }<a name="line.183"></a>
<span class="sourceLineNo">184</span>  }<a name="line.184"></a>
<span class="sourceLineNo">185</span><a name="line.185"></a>
<span class="sourceLineNo">186</span>  /**<a name="line.186"></a>
<span class="sourceLineNo">187</span>   * Associates {@code newValue} with {@code key} in this map, and returns the value previously<a name="line.187"></a>
<span class="sourceLineNo">188</span>   * associated with {@code key}, or zero if there was no such value.<a name="line.188"></a>
<span class="sourceLineNo">189</span>   */<a name="line.189"></a>
<span class="sourceLineNo">190</span>  public long put(K key, long newValue) {<a name="line.190"></a>
<span class="sourceLineNo">191</span>    outer: for (;;) {<a name="line.191"></a>
<span class="sourceLineNo">192</span>      AtomicLong atomic = map.get(key);<a name="line.192"></a>
<span class="sourceLineNo">193</span>      if (atomic == null) {<a name="line.193"></a>
<span class="sourceLineNo">194</span>        atomic = map.putIfAbsent(key, new AtomicLong(newValue));<a name="line.194"></a>
<span class="sourceLineNo">195</span>        if (atomic == null) {<a name="line.195"></a>
<span class="sourceLineNo">196</span>          return 0L;<a name="line.196"></a>
<span class="sourceLineNo">197</span>        }<a name="line.197"></a>
<span class="sourceLineNo">198</span>        // atomic is now non-null; fall through<a name="line.198"></a>
<span class="sourceLineNo">199</span>      }<a name="line.199"></a>
<span class="sourceLineNo">200</span><a name="line.200"></a>
<span class="sourceLineNo">201</span>      for (;;) {<a name="line.201"></a>
<span class="sourceLineNo">202</span>        long oldValue = atomic.get();<a name="line.202"></a>
<span class="sourceLineNo">203</span>        if (oldValue == 0L) {<a name="line.203"></a>
<span class="sourceLineNo">204</span>          // don't compareAndSet a zero<a name="line.204"></a>
<span class="sourceLineNo">205</span>          if (map.replace(key, atomic, new AtomicLong(newValue))) {<a name="line.205"></a>
<span class="sourceLineNo">206</span>            return 0L;<a name="line.206"></a>
<span class="sourceLineNo">207</span>          }<a name="line.207"></a>
<span class="sourceLineNo">208</span>          // atomic replaced<a name="line.208"></a>
<span class="sourceLineNo">209</span>          continue outer;<a name="line.209"></a>
<span class="sourceLineNo">210</span>        }<a name="line.210"></a>
<span class="sourceLineNo">211</span><a name="line.211"></a>
<span class="sourceLineNo">212</span>        if (atomic.compareAndSet(oldValue, newValue)) {<a name="line.212"></a>
<span class="sourceLineNo">213</span>          return oldValue;<a name="line.213"></a>
<span class="sourceLineNo">214</span>        }<a name="line.214"></a>
<span class="sourceLineNo">215</span>        // value changed<a name="line.215"></a>
<span class="sourceLineNo">216</span>      }<a name="line.216"></a>
<span class="sourceLineNo">217</span>    }<a name="line.217"></a>
<span class="sourceLineNo">218</span>  }<a name="line.218"></a>
<span class="sourceLineNo">219</span><a name="line.219"></a>
<span class="sourceLineNo">220</span>  /**<a name="line.220"></a>
<span class="sourceLineNo">221</span>   * Copies all of the mappings from the specified map to this map. The effect of this call is<a name="line.221"></a>
<span class="sourceLineNo">222</span>   * equivalent to that of calling {@code put(k, v)} on this map once for each mapping from key<a name="line.222"></a>
<span class="sourceLineNo">223</span>   * {@code k} to value {@code v} in the specified map. The behavior of this operation is undefined<a name="line.223"></a>
<span class="sourceLineNo">224</span>   * if the specified map is modified while the operation is in progress.<a name="line.224"></a>
<span class="sourceLineNo">225</span>   */<a name="line.225"></a>
<span class="sourceLineNo">226</span>  public void putAll(Map&lt;? extends K, ? extends Long&gt; m) {<a name="line.226"></a>
<span class="sourceLineNo">227</span>    for (Map.Entry&lt;? extends K, ? extends Long&gt; entry : m.entrySet()) {<a name="line.227"></a>
<span class="sourceLineNo">228</span>      put(entry.getKey(), entry.getValue());<a name="line.228"></a>
<span class="sourceLineNo">229</span>    }<a name="line.229"></a>
<span class="sourceLineNo">230</span>  }<a name="line.230"></a>
<span class="sourceLineNo">231</span><a name="line.231"></a>
<span class="sourceLineNo">232</span>  /**<a name="line.232"></a>
<span class="sourceLineNo">233</span>   * Removes and returns the value associated with {@code key}. If {@code key} is not<a name="line.233"></a>
<span class="sourceLineNo">234</span>   * in the map, this method has no effect and returns zero.<a name="line.234"></a>
<span class="sourceLineNo">235</span>   */<a name="line.235"></a>
<span class="sourceLineNo">236</span>  public long remove(K key) {<a name="line.236"></a>
<span class="sourceLineNo">237</span>    AtomicLong atomic = map.get(key);<a name="line.237"></a>
<span class="sourceLineNo">238</span>    if (atomic == null) {<a name="line.238"></a>
<span class="sourceLineNo">239</span>      return 0L;<a name="line.239"></a>
<span class="sourceLineNo">240</span>    }<a name="line.240"></a>
<span class="sourceLineNo">241</span><a name="line.241"></a>
<span class="sourceLineNo">242</span>    for (;;) {<a name="line.242"></a>
<span class="sourceLineNo">243</span>      long oldValue = atomic.get();<a name="line.243"></a>
<span class="sourceLineNo">244</span>      if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {<a name="line.244"></a>
<span class="sourceLineNo">245</span>        // only remove after setting to zero, to avoid concurrent updates<a name="line.245"></a>
<span class="sourceLineNo">246</span>        map.remove(key, atomic);<a name="line.246"></a>
<span class="sourceLineNo">247</span>        // succeed even if the remove fails, since the value was already adjusted<a name="line.247"></a>
<span class="sourceLineNo">248</span>        return oldValue;<a name="line.248"></a>
<span class="sourceLineNo">249</span>      }<a name="line.249"></a>
<span class="sourceLineNo">250</span>    }<a name="line.250"></a>
<span class="sourceLineNo">251</span>  }<a name="line.251"></a>
<span class="sourceLineNo">252</span><a name="line.252"></a>
<span class="sourceLineNo">253</span>  /**<a name="line.253"></a>
<span class="sourceLineNo">254</span>   * Removes all mappings from this map whose values are zero.<a name="line.254"></a>
<span class="sourceLineNo">255</span>   *<a name="line.255"></a>
<span class="sourceLineNo">256</span>   * &lt;p&gt;This method is not atomic: the map may be visible in intermediate states, where some<a name="line.256"></a>
<span class="sourceLineNo">257</span>   * of the zero values have been removed and others have not.<a name="line.257"></a>
<span class="sourceLineNo">258</span>   */<a name="line.258"></a>
<span class="sourceLineNo">259</span>  public void removeAllZeros() {<a name="line.259"></a>
<span class="sourceLineNo">260</span>    for (K key : map.keySet()) {<a name="line.260"></a>
<span class="sourceLineNo">261</span>      AtomicLong atomic = map.get(key);<a name="line.261"></a>
<span class="sourceLineNo">262</span>      if (atomic != null &amp;&amp; atomic.get() == 0L) {<a name="line.262"></a>
<span class="sourceLineNo">263</span>        map.remove(key, atomic);<a name="line.263"></a>
<span class="sourceLineNo">264</span>      }<a name="line.264"></a>
<span class="sourceLineNo">265</span>    }<a name="line.265"></a>
<span class="sourceLineNo">266</span>  }<a name="line.266"></a>
<span class="sourceLineNo">267</span><a name="line.267"></a>
<span class="sourceLineNo">268</span>  /**<a name="line.268"></a>
<span class="sourceLineNo">269</span>   * Returns the sum of all values in this map.<a name="line.269"></a>
<span class="sourceLineNo">270</span>   *<a name="line.270"></a>
<span class="sourceLineNo">271</span>   * &lt;p&gt;This method is not atomic: the sum may or may not include other concurrent operations.<a name="line.271"></a>
<span class="sourceLineNo">272</span>   */<a name="line.272"></a>
<span class="sourceLineNo">273</span>  public long sum() {<a name="line.273"></a>
<span class="sourceLineNo">274</span>    long sum = 0L;<a name="line.274"></a>
<span class="sourceLineNo">275</span>    for (AtomicLong value : map.values()) {<a name="line.275"></a>
<span class="sourceLineNo">276</span>      sum = sum + value.get();<a name="line.276"></a>
<span class="sourceLineNo">277</span>    }<a name="line.277"></a>
<span class="sourceLineNo">278</span>    return sum;<a name="line.278"></a>
<span class="sourceLineNo">279</span>  }<a name="line.279"></a>
<span class="sourceLineNo">280</span><a name="line.280"></a>
<span class="sourceLineNo">281</span>  private transient Map&lt;K, Long&gt; asMap;<a name="line.281"></a>
<span class="sourceLineNo">282</span><a name="line.282"></a>
<span class="sourceLineNo">283</span>  /**<a name="line.283"></a>
<span class="sourceLineNo">284</span>   * Returns a live, read-only view of the map backing this {@code AtomicLongMap}.<a name="line.284"></a>
<span class="sourceLineNo">285</span>   */<a name="line.285"></a>
<span class="sourceLineNo">286</span>  public Map&lt;K, Long&gt; asMap() {<a name="line.286"></a>
<span class="sourceLineNo">287</span>    Map&lt;K, Long&gt; result = asMap;<a name="line.287"></a>
<span class="sourceLineNo">288</span>    return (result == null) ? asMap = createAsMap() : result;<a name="line.288"></a>
<span class="sourceLineNo">289</span>  }<a name="line.289"></a>
<span class="sourceLineNo">290</span><a name="line.290"></a>
<span class="sourceLineNo">291</span>  private Map&lt;K, Long&gt; createAsMap() {<a name="line.291"></a>
<span class="sourceLineNo">292</span>    return Collections.unmodifiableMap(<a name="line.292"></a>
<span class="sourceLineNo">293</span>        Maps.transformValues(map, new Function&lt;AtomicLong, Long&gt;() {<a name="line.293"></a>
<span class="sourceLineNo">294</span>          @Override<a name="line.294"></a>
<span class="sourceLineNo">295</span>          public Long apply(AtomicLong atomic) {<a name="line.295"></a>
<span class="sourceLineNo">296</span>            return atomic.get();<a name="line.296"></a>
<span class="sourceLineNo">297</span>          }<a name="line.297"></a>
<span class="sourceLineNo">298</span>        }));<a name="line.298"></a>
<span class="sourceLineNo">299</span>  }<a name="line.299"></a>
<span class="sourceLineNo">300</span><a name="line.300"></a>
<span class="sourceLineNo">301</span>  /**<a name="line.301"></a>
<span class="sourceLineNo">302</span>   * Returns true if this map contains a mapping for the specified key.<a name="line.302"></a>
<span class="sourceLineNo">303</span>   */<a name="line.303"></a>
<span class="sourceLineNo">304</span>  public boolean containsKey(Object key) {<a name="line.304"></a>
<span class="sourceLineNo">305</span>    return map.containsKey(key);<a name="line.305"></a>
<span class="sourceLineNo">306</span>  }<a name="line.306"></a>
<span class="sourceLineNo">307</span><a name="line.307"></a>
<span class="sourceLineNo">308</span>  /**<a name="line.308"></a>
<span class="sourceLineNo">309</span>   * Returns the number of key-value mappings in this map. If the map contains more than<a name="line.309"></a>
<span class="sourceLineNo">310</span>   * {@code Integer.MAX_VALUE} elements, returns {@code Integer.MAX_VALUE}.<a name="line.310"></a>
<span class="sourceLineNo">311</span>   */<a name="line.311"></a>
<span class="sourceLineNo">312</span>  public int size() {<a name="line.312"></a>
<span class="sourceLineNo">313</span>    return map.size();<a name="line.313"></a>
<span class="sourceLineNo">314</span>  }<a name="line.314"></a>
<span class="sourceLineNo">315</span><a name="line.315"></a>
<span class="sourceLineNo">316</span>  /**<a name="line.316"></a>
<span class="sourceLineNo">317</span>   * Returns {@code true} if this map contains no key-value mappings.<a name="line.317"></a>
<span class="sourceLineNo">318</span>   */<a name="line.318"></a>
<span class="sourceLineNo">319</span>  public boolean isEmpty() {<a name="line.319"></a>
<span class="sourceLineNo">320</span>    return map.isEmpty();<a name="line.320"></a>
<span class="sourceLineNo">321</span>  }<a name="line.321"></a>
<span class="sourceLineNo">322</span><a name="line.322"></a>
<span class="sourceLineNo">323</span>  /**<a name="line.323"></a>
<span class="sourceLineNo">324</span>   * Removes all of the mappings from this map. The map will be empty after this call returns.<a name="line.324"></a>
<span class="sourceLineNo">325</span>   *<a name="line.325"></a>
<span class="sourceLineNo">326</span>   * &lt;p&gt;This method is not atomic: the map may not be empty after returning if there were concurrent<a name="line.326"></a>
<span class="sourceLineNo">327</span>   * writes.<a name="line.327"></a>
<span class="sourceLineNo">328</span>   */<a name="line.328"></a>
<span class="sourceLineNo">329</span>  public void clear() {<a name="line.329"></a>
<span class="sourceLineNo">330</span>    map.clear();<a name="line.330"></a>
<span class="sourceLineNo">331</span>  }<a name="line.331"></a>
<span class="sourceLineNo">332</span><a name="line.332"></a>
<span class="sourceLineNo">333</span>  @Override<a name="line.333"></a>
<span class="sourceLineNo">334</span>  public String toString() {<a name="line.334"></a>
<span class="sourceLineNo">335</span>    return map.toString();<a name="line.335"></a>
<span class="sourceLineNo">336</span>  }<a name="line.336"></a>
<span class="sourceLineNo">337</span><a name="line.337"></a>
<span class="sourceLineNo">338</span>  /*<a name="line.338"></a>
<span class="sourceLineNo">339</span>   * ConcurrentMap operations which we may eventually add.<a name="line.339"></a>
<span class="sourceLineNo">340</span>   *<a name="line.340"></a>
<span class="sourceLineNo">341</span>   * The problem with these is that remove(K, long) has to be done in two phases by definition ---<a name="line.341"></a>
<span class="sourceLineNo">342</span>   * first decrementing to zero, and then removing. putIfAbsent or replace could observe the<a name="line.342"></a>
<span class="sourceLineNo">343</span>   * intermediate zero-state. Ways we could deal with this are:<a name="line.343"></a>
<span class="sourceLineNo">344</span>   *<a name="line.344"></a>
<span class="sourceLineNo">345</span>   * - Don't define any of the ConcurrentMap operations. This is the current state of affairs.<a name="line.345"></a>
<span class="sourceLineNo">346</span>   *<a name="line.346"></a>
<span class="sourceLineNo">347</span>   * - Define putIfAbsent and replace as treating zero and absent identically (as currently<a name="line.347"></a>
<span class="sourceLineNo">348</span>   *   implemented below). This is a bit surprising with putIfAbsent, which really becomes<a name="line.348"></a>
<span class="sourceLineNo">349</span>   *   putIfZero.<a name="line.349"></a>
<span class="sourceLineNo">350</span>   *<a name="line.350"></a>
<span class="sourceLineNo">351</span>   * - Allow putIfAbsent and replace to distinguish between zero and absent, but don't implement<a name="line.351"></a>
<span class="sourceLineNo">352</span>   *   remove(K, long). Without any two-phase operations it becomes feasible for all remaining<a name="line.352"></a>
<span class="sourceLineNo">353</span>   *   operations to distinguish between zero and absent. If we do this, then perhaps we should add<a name="line.353"></a>
<span class="sourceLineNo">354</span>   *   replace(key, long).<a name="line.354"></a>
<span class="sourceLineNo">355</span>   *<a name="line.355"></a>
<span class="sourceLineNo">356</span>   * - Introduce a special-value private static final AtomicLong that would have the meaning of<a name="line.356"></a>
<span class="sourceLineNo">357</span>   *   removal-in-progress, and rework all operations to properly distinguish between zero and<a name="line.357"></a>
<span class="sourceLineNo">358</span>   *   absent.<a name="line.358"></a>
<span class="sourceLineNo">359</span>   */<a name="line.359"></a>
<span class="sourceLineNo">360</span><a name="line.360"></a>
<span class="sourceLineNo">361</span>  /**<a name="line.361"></a>
<span class="sourceLineNo">362</span>   * If {@code key} is not already associated with a value or if {@code key} is associated with<a name="line.362"></a>
<span class="sourceLineNo">363</span>   * zero, associate it with {@code newValue}. Returns the previous value associated with<a name="line.363"></a>
<span class="sourceLineNo">364</span>   * {@code key}, or zero if there was no mapping for {@code key}.<a name="line.364"></a>
<span class="sourceLineNo">365</span>   */<a name="line.365"></a>
<span class="sourceLineNo">366</span>  long putIfAbsent(K key, long newValue) {<a name="line.366"></a>
<span class="sourceLineNo">367</span>    for (;;) {<a name="line.367"></a>
<span class="sourceLineNo">368</span>      AtomicLong atomic = map.get(key);<a name="line.368"></a>
<span class="sourceLineNo">369</span>      if (atomic == null) {<a name="line.369"></a>
<span class="sourceLineNo">370</span>        atomic = map.putIfAbsent(key, new AtomicLong(newValue));<a name="line.370"></a>
<span class="sourceLineNo">371</span>        if (atomic == null) {<a name="line.371"></a>
<span class="sourceLineNo">372</span>          return 0L;<a name="line.372"></a>
<span class="sourceLineNo">373</span>        }<a name="line.373"></a>
<span class="sourceLineNo">374</span>        // atomic is now non-null; fall through<a name="line.374"></a>
<span class="sourceLineNo">375</span>      }<a name="line.375"></a>
<span class="sourceLineNo">376</span><a name="line.376"></a>
<span class="sourceLineNo">377</span>      long oldValue = atomic.get();<a name="line.377"></a>
<span class="sourceLineNo">378</span>      if (oldValue == 0L) {<a name="line.378"></a>
<span class="sourceLineNo">379</span>        // don't compareAndSet a zero<a name="line.379"></a>
<span class="sourceLineNo">380</span>        if (map.replace(key, atomic, new AtomicLong(newValue))) {<a name="line.380"></a>
<span class="sourceLineNo">381</span>          return 0L;<a name="line.381"></a>
<span class="sourceLineNo">382</span>        }<a name="line.382"></a>
<span class="sourceLineNo">383</span>        // atomic replaced<a name="line.383"></a>
<span class="sourceLineNo">384</span>        continue;<a name="line.384"></a>
<span class="sourceLineNo">385</span>      }<a name="line.385"></a>
<span class="sourceLineNo">386</span><a name="line.386"></a>
<span class="sourceLineNo">387</span>      return oldValue;<a name="line.387"></a>
<span class="sourceLineNo">388</span>    }<a name="line.388"></a>
<span class="sourceLineNo">389</span>  }<a name="line.389"></a>
<span class="sourceLineNo">390</span><a name="line.390"></a>
<span class="sourceLineNo">391</span>  /**<a name="line.391"></a>
<span class="sourceLineNo">392</span>   * If {@code (key, expectedOldValue)} is currently in the map, this method replaces<a name="line.392"></a>
<span class="sourceLineNo">393</span>   * {@code expectedOldValue} with {@code newValue} and returns true; otherwise, this method<a name="line.393"></a>
<span class="sourceLineNo">394</span>   * returns false.<a name="line.394"></a>
<span class="sourceLineNo">395</span>   *<a name="line.395"></a>
<span class="sourceLineNo">396</span>   * &lt;p&gt;If {@code expectedOldValue} is zero, this method will succeed if {@code (key, zero)}<a name="line.396"></a>
<span class="sourceLineNo">397</span>   * is currently in the map, or if {@code key} is not in the map at all.<a name="line.397"></a>
<span class="sourceLineNo">398</span>   */<a name="line.398"></a>
<span class="sourceLineNo">399</span>  boolean replace(K key, long expectedOldValue, long newValue) {<a name="line.399"></a>
<span class="sourceLineNo">400</span>    if (expectedOldValue == 0L) {<a name="line.400"></a>
<span class="sourceLineNo">401</span>      return putIfAbsent(key, newValue) == 0L;<a name="line.401"></a>
<span class="sourceLineNo">402</span>    } else {<a name="line.402"></a>
<span class="sourceLineNo">403</span>      AtomicLong atomic = map.get(key);<a name="line.403"></a>
<span class="sourceLineNo">404</span>      return (atomic == null) ? false : atomic.compareAndSet(expectedOldValue, newValue);<a name="line.404"></a>
<span class="sourceLineNo">405</span>    }<a name="line.405"></a>
<span class="sourceLineNo">406</span>  }<a name="line.406"></a>
<span class="sourceLineNo">407</span><a name="line.407"></a>
<span class="sourceLineNo">408</span>  /**<a name="line.408"></a>
<span class="sourceLineNo">409</span>   * If {@code (key, value)} is currently in the map, this method removes it and returns<a name="line.409"></a>
<span class="sourceLineNo">410</span>   * true; otherwise, this method returns false.<a name="line.410"></a>
<span class="sourceLineNo">411</span>   */<a name="line.411"></a>
<span class="sourceLineNo">412</span>  boolean remove(K key, long value) {<a name="line.412"></a>
<span class="sourceLineNo">413</span>    AtomicLong atomic = map.get(key);<a name="line.413"></a>
<span class="sourceLineNo">414</span>    if (atomic == null) {<a name="line.414"></a>
<span class="sourceLineNo">415</span>      return false;<a name="line.415"></a>
<span class="sourceLineNo">416</span>    }<a name="line.416"></a>
<span class="sourceLineNo">417</span><a name="line.417"></a>
<span class="sourceLineNo">418</span>    long oldValue = atomic.get();<a name="line.418"></a>
<span class="sourceLineNo">419</span>    if (oldValue != value) {<a name="line.419"></a>
<span class="sourceLineNo">420</span>      return false;<a name="line.420"></a>
<span class="sourceLineNo">421</span>    }<a name="line.421"></a>
<span class="sourceLineNo">422</span><a name="line.422"></a>
<span class="sourceLineNo">423</span>    if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {<a name="line.423"></a>
<span class="sourceLineNo">424</span>      // only remove after setting to zero, to avoid concurrent updates<a name="line.424"></a>
<span class="sourceLineNo">425</span>      map.remove(key, atomic);<a name="line.425"></a>
<span class="sourceLineNo">426</span>      // succeed even if the remove fails, since the value was already adjusted<a name="line.426"></a>
<span class="sourceLineNo">427</span>      return true;<a name="line.427"></a>
<span class="sourceLineNo">428</span>    }<a name="line.428"></a>
<span class="sourceLineNo">429</span><a name="line.429"></a>
<span class="sourceLineNo">430</span>    // value changed<a name="line.430"></a>
<span class="sourceLineNo">431</span>    return false;<a name="line.431"></a>
<span class="sourceLineNo">432</span>  }<a name="line.432"></a>
<span class="sourceLineNo">433</span><a name="line.433"></a>
<span class="sourceLineNo">434</span>}<a name="line.434"></a>




























































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